The main objectives of the proposed project are: (1) to investigate at the molecular level the enzyme mechanisms that regulate carbohydrate synthesis, with particular reference to organelles and cells in which this process is a dominant biosynthetic pathway; and (2) to determine the extent to which such regulatory mechanisms are applicable to glucogenesis in general. The specific aims of the project are: (a) to exploit and develop two recent findings of our laboratory on the regulation of carbohydrate synthesis, i.e., the activation by reduced ferredoxin of the fructose diphosphatase (FDPase) of chloroplasts and the activation by fructose 6- phosphate and deactivation by fructose diphosphate of ribulose diphosphate carboxylase at a physiological concentration of CO2; (b) to purify the protein factor component of the chloroplast FDPase system and determine its regulatory role; (c) to investigate the nature of regulatory mechanisms of carbohydrate synthesis in different types of cells, including photosynthetic bacteria which appear to lack the reductive pentose phosphate cycle.